In the field of ultrasound medical imaging, displayed images are used which are actually a combination of two images. A first displayed image is a monochrome image which shows all stationary structures and some strong reflecting moving structures detected by the ultrasound apparatus. A second image, superimposed on the first, depicts all material detected by the ultrasound apparatus using more sensitive Doppler motion techniques. This second image is displayed in color on the display monitor to allow it to be discerned from the monochrome image.
A common use of the motion detection provided by the color flow image is in the detection of blood flow. Accurate detection of blood flow is desirable in many ultrasound examination procedures such as a cardiac examination or examination of the carotid artery. However, a recurring problem in color flow detection is the display of large areas of color arising from either spurious or unwanted motion detections. These large areas of color are commonly referred to as "flash", and can arise from movement of the ultrasound probe or from movement of the tissue within a patient's body. The unwanted flash usually makes it difficult or impossible to discern desired regions of color flow, and often obscures the monochrome image as well.